What we’re talking about when we talk about Gerrymandering

Early in October, the Supreme Court heard a case about partisan gerrymandering. In sum, the plaintiff alleged that the GOP purposefully drew congressional districts to waste and dilute democratic votes, thereby punishing those who registered democratic by making their vote count less.

Gerrymandering has been an issue since there have been representative republics, since there is no universal definition of “good” and “proper,” especially when it comes to divvying up voters into districts. Despite there being countless incidents in which those with the power to redraw lines dilute the voting power of the opposition party to render their vote essentially wasted, it’s been hard to prove beyond a shadow of a doubt that the lines intentionally suppress the voices of opposing voters. The Supreme Court has entertained a number of rubrics and measuring sticks to benchmark gerrymandering, but none have withstood the harsh scrutiny of the justices, particularly Kennedy.

This term, though, the Court heard a case that offers a rubric for determining whether gerrymandering has occurred. Researchers have been working hard on the most accurate measuring stick for partisan (that is, political affiliation) and racial gerrymandering, and the equation they’ve come up with is called the Efficiency Gap.

The Efficiency Gap measures the number of “wasted” votes on either side of a political party line. On the RadioLab spinoff podcast More Perfect, the researchers discussed what it means for a vote to count as wasted. In a two-party system, voters have two options, and the person with the most votes wins. Imagine we have a district in which sixty percent of the voters opt for the GOP, and forty percent cast votes for the Democratic candidate. Since either party only needs fifty percent of the votes to win, any vote past fifty percent counts as wasted — so in this case, ten percent of the GOP votes are wasted. Then, all the votes cast for the losing party are also considered “wasted,” since they didn’t bring anyone into office.

To calculate the efficiency gap for a state, take the wasted votes of one party, subtract the wasted votes of the other party, and divide by the total number of voters. The number that equation produces measures how balanced the number of wasted votes per party is. If the number is large, that means that one party’s votes are wasted at a higher proportion than the other’s is, but a small number means that the districts are drawn pretty fairly.

SCOTUS will likely be handing down a ruling this spring, but all eyes are on Kennedy, the swing vote. Gill v Whitford is an attempt to outlaw gerrymandering once and for all.